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The U.S. military has spent about $1 billion so far and played a far larger role in Libya than it has acknowledged, quietly implementing an emerging "covert intervention" strategy that the Obama administration hopes will let America fight small wars with a barely detectable footprint.

Officially, President Obama handed the lead role of ousting Muammar Gaddafi to the European members of NATO. For this he was criticized by Washington war hawks who suggested that Europeans working with a ragtag team of Libyan rebels was a recipe for stalemate, not victory.

But behind the scenes, the U.S. military played an indispensable role in the Libya campaign, deploying far more forces than the administration chose to advertise. And at NATO headquarters outside Brussels, the U.S. was intimately involved in all decisions about how the Libyan rebels should be supported as they rolled up control of cities and oil refineries and marched toward the capital, Tripoli.

The Libya campaign was a unique international effort: 15 European nations working with the U.S. and three Arab nations. The air offensive was launched from 29 airbases in six European countries. But only six European nations joined with the U.S. and Canada to fly strikes against Gaddafi’s forces. The scale of the unpublicized U.S. role affirms hawks’ arguments: a divided NATO simply couldn’t have waged the war it did without extensive American help. What the hawks underestimated was the U.S. ability to operate without publicity—in military lingo, beneath the radar.

According to two senior NATO officials, one American and the other European, these were the critical U.S. contributions during the six-month military campaign:

• An international naval force gathered off Libya. To lower the U.S. profile, the administration elected not to send a supercarrier. Even so, the dozen U.S. warships on station were the biggest contingent in this armada. In the opening hours of the campaign, an American submarine, the USS Florida, launched 100 cruise missiles against Libyan air defenses, crucially opening an entry corridor for the airstrikes that followed.

• U.S. tanker aircraft refueled European aircraft on the great majority of missions against Gaddafi’s forces. The Europeans have tanker aircraft, but not enough to support a 24/7 air offensive averaging, by NATO count, around 100 missions a day, some 50 of them strike sorties. The U.S. flew 30 of the 40 tankers.

• When the Europeans ran low on precision-attack munitions, the U.S. quietly resupplied them. (That explains why European air forces flying F-16s—those of Norway, Denmark, Belgium—carried out a disproportionate share of the strikes in the early phase of the campaign. The U.S. had stocks of the munitions to resupply them. When Britain and France, which fly European-built strike aircraft, also ran short, they couldn’t use U.S.-made bombs until they had made hurried modifications to their aircraft.)

• To target Gaddafi’s military, NATO largely relied on U.S. JSTARS surveillance aircraft, which, flying offshore, could track the movements of rival forces. When more detailed targeting information was needed—as in the battles for Misrata and other towns defended by Gaddafi’s troops—the U.S. flew Predator drones to relay a block-by-block picture.

• U.S. Air Force targeting specialists were in NATO’s Naples operational headquarters throughout the campaign. They oversaw the preparing of “target folders” for the strikes in Tripoli against Gaddafi’s compound and the headquarters of his military and intelligence services. (Organizing precision strikes by high-speed jets is not a task for novices. The attack routes over Tripoli and the release times of bombs had to be precisely calibrated so munitions released even a second late by a strike aircraft would have the best chance of avoiding civilian homes.)

• U.S. AWACS aircraft, high over the Mediterranean, handled much of the battle-management task, acting as air-traffic controllers on most of the strike missions. Again, the Europeans have AWACS, but not enough crews to handle an all-hours campaign lasting months.

• Eavesdropping by U.S. intelligence—some by aircraft, some by a listening post quietly established just outside Libya—gave NATO unparalleled knowledge of what Gaddafi’s military planned.

• All this was crucial in supporting the European effort. But U.S. involvement went way beyond that. In all, the U.S. had flown by late August more than 5,300 missions, by Pentagon count. More than 1,200 of these were strike sorties against Libyan targets.

• The administration largely stuck to Obama’s decision that the U.S. would not put boots on the ground in Libya (although the CIA did have agents inside Tripoli). British and French special forces were on the ground, training and organizing the insurgents—as were units from two Arab nations, Qatar and Jordan. But their communications relied on a satellite channel run by the U.S. And the U.S. also supplied other high-tech gear—NATO sources declined to describe it, but apparently it had never been given before, even to allied special forces.

• When a desperate Gaddafi began to launch Scud missiles into towns held by the opposition, a U.S. guided-missile destroyer offshore negated his offensive by shooting down the Scuds.

“President Obama may have taken the U.S. out of the direct combat role, but he certainly did not take American forces out of the front line,” Michael Clarke, director of the Royal United Services Institute think tank, wrote in a recent analysis. “The European allies were hardly ‘going it alone’ in this operation.”

With the Pentagon facing deep budget cuts, the Libyan campaign will likely provoke a debate in Washington. There is zero appetite to repeat the massive interventions in Iraq and Afghanistan, where the U.S. is still embroiled a decade later. The Libya campaign appears to offer an alternative. It hasn’t been cheap. The Pentagon estimates U.S. operations there cost $896 million through the end of July.

The good news is that the U.S. will be repaid for its assistance to the Europeans—everything from fuel for the aircraft to munitions and spare parts—which cost a further $222 million, the Pentagon estimates. And compared with Afghanistan, which is still costing the U.S. taxpayer roughly $10 billion a month, Gaddafi’s overthrow has been a bargain.

One senior NATO official pointed to the U.S. invasion of Afghanistan at the end of 2001 as a precursor of the Libya campaign. In Afghanistan, U.S. special forces riding with Northern Alliance troops downloaded on their laptops satellite pictures of Taliban deployments over the next hill, and used their satphones and hand-held GPS targeting devices to call in airstrikes. The Taliban was overthrown in 63 days.

“That was a classic example of the U.S. using its technological supremacy to support local forces,” the official said. “Now we have Libya as another example.”

The campaign in Yemen provides a third example. For more than two years, U.S. special forces have been training and working with Yemeni troops to combat, among other insurgent groups, Al Qaeda in the Arabian Peninsula (AQAP). The U.S. campaign in Yemen has used conventional weaponry on occasion: sorties by Harriers and even some cruise-missile strikes. But the burden of much of the campaign has fallen to special-forces units, supported by Predators.

The ongoing struggle in Pakistan is arguably yet another case study in what seems to be evolving as a new American way of war.

Predator strikes against alleged Taliban and allied Afghan insurgent groups massing in Pakistan have preoccupied international attention. But senior NATO officers in Kabul whisper that again “beneath the radar,” CIA paramilitary operatives are inside Pakistan, leading groups of locally recruited frontier tribesmen. They apparently supply much of the targeting information for the Predators—especially against senior Taliban and al Qaeda operatives, who reportedly are the main targets of these CIA-led bands. Their mission may go beyond reconnaissance. According to one senior NATO officer in Kabul, some strikes credited to Predators actually result from raids by this covert force.

The killing 10 days ago of al Qaeda’s operations chief, Atiyah Abd al-Rahman, in the Pakistani frontier province of Waziristan, was the greatest single success in the campaign. U.S. officials attributed al-Rahman’s death to a Predator strike. But on the question of how he was identified and tracked, the officials were tight-lipped.